1. Field of the Invention
This invention relates to a recording medium, and more particularly to a disc having an identification information for indicating whether a single-sided or a double-sided recording layer exists. Also, this invention is directed to a disc recording control method for controlling a recording of data in accordance with whether a disc has a single-sided or a double-sided recording layer.
2. Description of the Prior Art
Generally, a disc can be classified into three types, such as a read-only memory (ROM) type, a write once read many (WORM) type and a rewritable type capable of a repetitive recording, depending upon whether or not it has a repetitive recording ability. The ROM type disc includes a CD (compact disc)-ROM and a DVD (digital versatile disc)-ROM, etc., and the WORM type disc includes a CD-R (recordable) and a DVD-R (recordable). On the other hand, the rewritable disc includes a CD-RW (rewritable), a DVD-RW (rewritable), DVD-RAM and a magneto-optical disc (MOD), etc.
Further, a disc may be classified as a single-sided disc or a double-sided disc in accordance with its structure. As shown in FIG. 1, a single-sided disc consists of a single-sided recording layer 10 disposed between a transparent substrate 12 and a dummy substrate 14 and has a thickness of 1.2 mm. Such a single-sided disc allows a laser light beam to be irradiated, via the transparent substrate 12, onto the recording layer 10 so as to access data. In contrast, the double-sided disc has two recording layers 10A and 10B disposed between a first substrate 12A and a second substrate 12B. The first recording layer 10A allows data to be accessed by a light beam received via the first substrate 12A while the second recording layer 10B allows data to be accessed by a light beam received via the second substrate 12B. The double-sided disc with such double-sided recording layers 10A and 10B is capable of recording data equal to twice the recording capacity of the single-sided disc. However, the data recorded on each side of the double-sided disc is not continued because the double-sided disc is presently only a two single-sided discs joined together. This is caused by the fact that the double-sided disc is not distinguished from the single-sided disc by means of a disc driving apparatus. In order to assure a continuity of data in the double-sided disc, the disc requires identification information for indicating whether the single-sided or the double-sided recording layer exists.
When the rewritable disc experiences several recording/reproduction operations, its recording layer may deteriorate. Also, in the rewritable disc, unwritable defect regions due to a deterioration of the recording layer, a scratch on the surface, fingerprints and dust, etc. may occur over a considerable range of effective recording area. In order to overcome such problems, the rewritable type disc is stored within a cartridge for protecting it from exterior contamination sources and impact. Such a cartridge is largely classified into a sealed type and an open-closed type depending upon whether or not it can be opened and closed. The sealed type cartridge is applicable to both the single-sided disc and the double-sided disc, whereas the open-closed type cartridge is preferably applied to only the single-sided disc. The open-closed type cartridge has a structure that allows a user to easily insert or take out a disc. In other words, a disc to be received within the open-closed type cartridge can be removed from the cartridge (a "bare disc"). Since such two types of cartridges have the same external shape, they can be identified by the opening or closing of sensor holes 16 as shown in FIG. 3. In other words, a disc driving apparatus recognizes the two types of cartridges depending upon whether the sensor holes 16 have been opened or closed.
As described above, use of the rewritable disc is liable to generate an error at the time of recording or reproduction because defect areas develop with use. Due to this, the rewritable disc is subject to a verification upon recording. Such a verification is to detect any defects in the recording region by recording a test data onto an area for recording and reproducing the recorded test data, and then by checking if the reproduced data is identical to the recorded data. Position information for the defective recording area is usually recorded on a lead-in area and so forth. Accordingly, the disc driving apparatus refers to the position information for defective areas to be recorded on the lead-in area and so forth during the recording and reproduction of information, and manages the defective areas. The defective areas have a higher probability to be generated at a disc received within the open-closed type cartridge rather than within the sealed type cartridge. Therefore, a recording of information is performed without verification for a disc received within the sealed type cartridge, whereas it is preferably performed after verification for a disc received within the open-closed type cartridge. Furthermore, the double-sided disc is liable to be contaminated relative to the single-sided disc by fingerprints and dust, etc. when it is taken out from the cartridge. In view of this, it is desirable that the double-sided disc should not be received within the open-closed type cartridge. The need for verification according to the type of cartridge and the type of disc can be described in the following Table 1.
TABLE 1 Disc Type Single-sided Double-sided Disc Disc Cartridge Sealed Type Verification Verification Type (X) (X) Open-Closed Type (Including Bare Verification (X) Disc) (O)
As seen from the Table 1, the sealed type cartridge permits a recording of information to be performed without a verification because it restricts the external exposure of a disc absolutely, whereas the open-closed type cartridge involving the state of a bare disc must be necessarily verified prior to a recording of information because a disc may be exposed to outside elements. Accordingly, the disc driving apparatus verifies a disc type depending on the two types of cartridges.
However, the double-sided disc received only within the sealed type cartridge may be used in a state of bare disc or may be used in a state received within the open-closed type cartridge due to a user's intentional destruction of sealed type cartridge. In this case, the double-sided disc occurs driving errors because it is dealt with the bare type single-sided disc or the open-closed type cartridge by the disc driving apparatus. Also, since the double-sided disc exposed to the outside occurs many defective areas by fingerprints and dust, etc., it must waste a longer time than the single-sided disc when it is verified like the single-sided disc.